fs/fscache/object.c

   1 /* FS-Cache object state machine handler
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * See Documentation/filesystems/caching/object.txt for a description of the
  12  * object state machine and the in-kernel representations.
  13  */
  14
  15 #define FSCACHE_DEBUG_LEVEL COOKIE
  16 #include <linux/module.h>
  17 #include "internal.h"
  18
  19 const char *fscache_object_states[] = {
  20         [FSCACHE_OBJECT_INIT]           = "OBJECT_INIT",
  21         [FSCACHE_OBJECT_LOOKING_UP]     = "OBJECT_LOOKING_UP",
  22         [FSCACHE_OBJECT_CREATING]       = "OBJECT_CREATING",
  23         [FSCACHE_OBJECT_AVAILABLE]      = "OBJECT_AVAILABLE",
  24         [FSCACHE_OBJECT_ACTIVE]         = "OBJECT_ACTIVE",
  25         [FSCACHE_OBJECT_UPDATING]       = "OBJECT_UPDATING",
  26         [FSCACHE_OBJECT_DYING]          = "OBJECT_DYING",
  27         [FSCACHE_OBJECT_LC_DYING]       = "OBJECT_LC_DYING",
  28         [FSCACHE_OBJECT_ABORT_INIT]     = "OBJECT_ABORT_INIT",
  29         [FSCACHE_OBJECT_RELEASING]      = "OBJECT_RELEASING",
  30         [FSCACHE_OBJECT_RECYCLING]      = "OBJECT_RECYCLING",
  31         [FSCACHE_OBJECT_WITHDRAWING]    = "OBJECT_WITHDRAWING",
  32         [FSCACHE_OBJECT_DEAD]           = "OBJECT_DEAD",
  33 };
  34 EXPORT_SYMBOL(fscache_object_states);
  35
  36 static void fscache_object_slow_work_put_ref(struct slow_work *);
  37 static int  fscache_object_slow_work_get_ref(struct slow_work *);
  38 static void fscache_object_slow_work_execute(struct slow_work *);
  39 static void fscache_initialise_object(struct fscache_object *);
  40 static void fscache_lookup_object(struct fscache_object *);
  41 static void fscache_object_available(struct fscache_object *);
  42 static void fscache_release_object(struct fscache_object *);
  43 static void fscache_withdraw_object(struct fscache_object *);
  44 static void fscache_enqueue_dependents(struct fscache_object *);
  45 static void fscache_dequeue_object(struct fscache_object *);
  46
  47 const struct slow_work_ops fscache_object_slow_work_ops = {
  48         .owner          = THIS_MODULE,
  49         .get_ref        = fscache_object_slow_work_get_ref,
  50         .put_ref        = fscache_object_slow_work_put_ref,
  51         .execute        = fscache_object_slow_work_execute,
  52 };
  53 EXPORT_SYMBOL(fscache_object_slow_work_ops);
  54
  55 /*
  56  * we need to notify the parent when an op completes that we had outstanding
  57  * upon it
  58  */
  59 static inline void fscache_done_parent_op(struct fscache_object *object)
  60 {
  61         struct fscache_object *parent = object->parent;
  62
  63         _enter("OBJ%x {OBJ%x,%x}",
  64                object->debug_id, parent->debug_id, parent->n_ops);
  65
  66         spin_lock_nested(&parent->lock, 1);
  67         parent->n_ops--;
  68         parent->n_obj_ops--;
  69         if (parent->n_ops == 0)
  70                 fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
  71         spin_unlock(&parent->lock);
  72 }
  73
  74 /*
  75  * process events that have been sent to an object's state machine
  76  * - initiates parent lookup
  77  * - does object lookup
  78  * - does object creation
  79  * - does object recycling and retirement
  80  * - does object withdrawal
  81  */
  82 static void fscache_object_state_machine(struct fscache_object *object)
  83 {
  84         enum fscache_object_state new_state;
  85
  86         ASSERT(object != NULL);
  87
  88         _enter("{OBJ%x,%s,%lx}",
  89                object->debug_id, fscache_object_states[object->state],
  90                object->events);
  91
  92         switch (object->state) {
  93                 /* wait for the parent object to become ready */
  94         case FSCACHE_OBJECT_INIT:
  95                 object->event_mask =
  96                         ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
  97                 fscache_initialise_object(object);
  98                 goto done;
  99
 100                 /* look up the object metadata on disk */
 101         case FSCACHE_OBJECT_LOOKING_UP:
 102                 fscache_lookup_object(object);
 103                 goto lookup_transit;
 104
 105                 /* create the object metadata on disk */
 106         case FSCACHE_OBJECT_CREATING:
 107                 fscache_lookup_object(object);
 108                 goto lookup_transit;
 109
 110                 /* handle an object becoming available; start pending
 111                  * operations and queue dependent operations for processing */
 112         case FSCACHE_OBJECT_AVAILABLE:
 113                 fscache_object_available(object);
 114                 goto active_transit;
 115
 116                 /* normal running state */
 117         case FSCACHE_OBJECT_ACTIVE:
 118                 goto active_transit;
 119
 120                 /* update the object metadata on disk */
 121         case FSCACHE_OBJECT_UPDATING:
 122                 clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
 123                 fscache_stat(&fscache_n_updates_run);
 124                 object->cache->ops->update_object(object);
 125                 goto active_transit;
 126
 127                 /* handle an object dying during lookup or creation */
 128         case FSCACHE_OBJECT_LC_DYING:
 129                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 130                 object->cache->ops->lookup_complete(object);
 131
 132                 spin_lock(&object->lock);
 133                 object->state = FSCACHE_OBJECT_DYING;
 134                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 135                                        &object->cookie->flags))
 136                         wake_up_bit(&object->cookie->flags,
 137                                     FSCACHE_COOKIE_CREATING);
 138                 spin_unlock(&object->lock);
 139
 140                 fscache_done_parent_op(object);
 141
 142                 /* wait for completion of all active operations on this object
 143                  * and the death of all child objects of this object */
 144         case FSCACHE_OBJECT_DYING:
 145         dying:
 146                 clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
 147                 spin_lock(&object->lock);
 148                 _debug("dying OBJ%x {%d,%d}",
 149                        object->debug_id, object->n_ops, object->n_children);
 150                 if (object->n_ops == 0 && object->n_children == 0) {
 151                         object->event_mask &=
 152                                 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
 153                         object->event_mask |=
 154                                 (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 155                                 (1 << FSCACHE_OBJECT_EV_RETIRE) |
 156                                 (1 << FSCACHE_OBJECT_EV_RELEASE) |
 157                                 (1 << FSCACHE_OBJECT_EV_ERROR);
 158                 } else {
 159                         object->event_mask &=
 160                                 ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 161                                   (1 << FSCACHE_OBJECT_EV_RETIRE) |
 162                                   (1 << FSCACHE_OBJECT_EV_RELEASE) |
 163                                   (1 << FSCACHE_OBJECT_EV_ERROR));
 164                         object->event_mask |=
 165                                 1 << FSCACHE_OBJECT_EV_CLEARED;
 166                 }
 167                 spin_unlock(&object->lock);
 168                 fscache_enqueue_dependents(object);
 169                 goto terminal_transit;
 170
 171                 /* handle an abort during initialisation */
 172         case FSCACHE_OBJECT_ABORT_INIT:
 173                 _debug("handle abort init %lx", object->events);
 174                 object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
 175
 176                 spin_lock(&object->lock);
 177                 fscache_dequeue_object(object);
 178
 179                 object->state = FSCACHE_OBJECT_DYING;
 180                 if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
 181                                        &object->cookie->flags))
 182                         wake_up_bit(&object->cookie->flags,
 183                                     FSCACHE_COOKIE_CREATING);
 184                 spin_unlock(&object->lock);
 185                 goto dying;
 186
 187                 /* handle the netfs releasing an object and possibly marking it
 188                  * obsolete too */
 189         case FSCACHE_OBJECT_RELEASING:
 190         case FSCACHE_OBJECT_RECYCLING:
 191                 object->event_mask &=
 192                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 193                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 194                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 195                           (1 << FSCACHE_OBJECT_EV_ERROR));
 196                 fscache_release_object(object);
 197                 spin_lock(&object->lock);
 198                 object->state = FSCACHE_OBJECT_DEAD;
 199                 spin_unlock(&object->lock);
 200                 fscache_stat(&fscache_n_object_dead);
 201                 goto terminal_transit;
 202
 203                 /* handle the parent cache of this object being withdrawn from
 204                  * active service */
 205         case FSCACHE_OBJECT_WITHDRAWING:
 206                 object->event_mask &=
 207                         ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
 208                           (1 << FSCACHE_OBJECT_EV_RETIRE) |
 209                           (1 << FSCACHE_OBJECT_EV_RELEASE) |
 210                           (1 << FSCACHE_OBJECT_EV_ERROR));
 211                 fscache_withdraw_object(object);
 212                 spin_lock(&object->lock);
 213                 object->state = FSCACHE_OBJECT_DEAD;
 214                 spin_unlock(&object->lock);
 215                 fscache_stat(&fscache_n_object_dead);
 216                 goto terminal_transit;
 217
 218                 /* complain about the object being woken up once it is
 219                  * deceased */
 220         case FSCACHE_OBJECT_DEAD:
 221                 printk(KERN_ERR "FS-Cache:"
 222                        " Unexpected event in dead state %lx\n",
 223                        object->events & object->event_mask);
 224                 BUG();
 225
 226         default:
 227                 printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
 228                        object->state);
 229                 BUG();
 230         }
 231
 232         /* determine the transition from a lookup state */
 233 lookup_transit:
 234         switch (fls(object->events & object->event_mask) - 1) {
 235         case FSCACHE_OBJECT_EV_WITHDRAW:
 236         case FSCACHE_OBJECT_EV_RETIRE:
 237         case FSCACHE_OBJECT_EV_RELEASE:
 238         case FSCACHE_OBJECT_EV_ERROR:
 239                 new_state = FSCACHE_OBJECT_LC_DYING;
 240                 goto change_state;
 241         case FSCACHE_OBJECT_EV_REQUEUE:
 242                 goto done;
 243         case -1:
 244                 goto done; /* sleep until event */
 245         default:
 246                 goto unsupported_event;
 247         }
 248
 249         /* determine the transition from an active state */
 250 active_transit:
 251         switch (fls(object->events & object->event_mask) - 1) {
 252         case FSCACHE_OBJECT_EV_WITHDRAW:
 253         case FSCACHE_OBJECT_EV_RETIRE:
 254         case FSCACHE_OBJECT_EV_RELEASE:
 255         case FSCACHE_OBJECT_EV_ERROR:
 256                 new_state = FSCACHE_OBJECT_DYING;
 257                 goto change_state;
 258         case FSCACHE_OBJECT_EV_UPDATE:
 259                 new_state = FSCACHE_OBJECT_UPDATING;
 260                 goto change_state;
 261         case -1:
 262                 new_state = FSCACHE_OBJECT_ACTIVE;
 263                 goto change_state; /* sleep until event */
 264         default:
 265                 goto unsupported_event;
 266         }
 267
 268         /* determine the transition from a terminal state */
 269 terminal_transit:
 270         switch (fls(object->events & object->event_mask) - 1) {
 271         case FSCACHE_OBJECT_EV_WITHDRAW:
 272                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 273                 goto change_state;
 274         case FSCACHE_OBJECT_EV_RETIRE:
 275                 new_state = FSCACHE_OBJECT_RECYCLING;
 276                 goto change_state;
 277         case FSCACHE_OBJECT_EV_RELEASE:
 278                 new_state = FSCACHE_OBJECT_RELEASING;
 279                 goto change_state;
 280         case FSCACHE_OBJECT_EV_ERROR:
 281                 new_state = FSCACHE_OBJECT_WITHDRAWING;
 282                 goto change_state;
 283         case FSCACHE_OBJECT_EV_CLEARED:
 284                 new_state = FSCACHE_OBJECT_DYING;
 285                 goto change_state;
 286         case -1:
 287                 goto done; /* sleep until event */
 288         default:
 289                 goto unsupported_event;
 290         }
 291
 292 change_state:
 293         spin_lock(&object->lock);
 294         object->state = new_state;
 295         spin_unlock(&object->lock);
 296
 297 done:
 298         _leave(" [->%s]", fscache_object_states[object->state]);
 299         return;
 300
 301 unsupported_event:
 302         printk(KERN_ERR "FS-Cache:"
 303                " Unsupported event %lx [mask %lx] in state %s\n",
 304                object->events, object->event_mask,
 305                fscache_object_states[object->state]);
 306         BUG();
 307 }
 308
 309 /*
 310  * execute an object
 311  */
 312 static void fscache_object_slow_work_execute(struct slow_work *work)
 313 {
 314         struct fscache_object *object =
 315                 container_of(work, struct fscache_object, work);
 316         unsigned long start;
 317
 318         _enter("{OBJ%x}", object->debug_id);
 319
 320         clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 321
 322         start = jiffies;
 323         fscache_object_state_machine(object);
 324         fscache_hist(fscache_objs_histogram, start);
 325         if (object->events & object->event_mask)
 326                 fscache_enqueue_object(object);
 327 }
 328
 329 /*
 330  * initialise an object
 331  * - check the specified object's parent to see if we can make use of it
 332  *   immediately to do a creation
 333  * - we may need to start the process of creating a parent and we need to wait
 334  *   for the parent's lookup and creation to complete if it's not there yet
 335  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 336  *   leaf-most cookies of the object and all its children
 337  */
 338 static void fscache_initialise_object(struct fscache_object *object)
 339 {
 340         struct fscache_object *parent;
 341
 342         _enter("");
 343         ASSERT(object->cookie != NULL);
 344         ASSERT(object->cookie->parent != NULL);
 345         ASSERT(list_empty(&object->work.link));
 346
 347         if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
 348                               (1 << FSCACHE_OBJECT_EV_RELEASE) |
 349                               (1 << FSCACHE_OBJECT_EV_RETIRE) |
 350                               (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
 351                 _debug("abort init %lx", object->events);
 352                 spin_lock(&object->lock);
 353                 object->state = FSCACHE_OBJECT_ABORT_INIT;
 354                 spin_unlock(&object->lock);
 355                 return;
 356         }
 357
 358         spin_lock(&object->cookie->lock);
 359         spin_lock_nested(&object->cookie->parent->lock, 1);
 360
 361         parent = object->parent;
 362         if (!parent) {
 363                 _debug("no parent");
 364                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 365         } else {
 366                 spin_lock(&object->lock);
 367                 spin_lock_nested(&parent->lock, 1);
 368                 _debug("parent %s", fscache_object_states[parent->state]);
 369
 370                 if (parent->state >= FSCACHE_OBJECT_DYING) {
 371                         _debug("bad parent");
 372                         set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 373                 } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
 374                         _debug("wait");
 375
 376                         /* we may get woken up in this state by child objects
 377                          * binding on to us, so we need to make sure we don't
 378                          * add ourself to the list multiple times */
 379                         if (list_empty(&object->dep_link)) {
 380                                 object->cache->ops->grab_object(object);
 381                                 list_add(&object->dep_link,
 382                                          &parent->dependents);
 383
 384                                 /* fscache_acquire_non_index_cookie() uses this
 385                                  * to wake the chain up */
 386                                 if (parent->state == FSCACHE_OBJECT_INIT)
 387                                         fscache_enqueue_object(parent);
 388                         }
 389                 } else {
 390                         _debug("go");
 391                         parent->n_ops++;
 392                         parent->n_obj_ops++;
 393                         object->lookup_jif = jiffies;
 394                         object->state = FSCACHE_OBJECT_LOOKING_UP;
 395                         set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 396                 }
 397
 398                 spin_unlock(&parent->lock);
 399                 spin_unlock(&object->lock);
 400         }
 401
 402         spin_unlock(&object->cookie->parent->lock);
 403         spin_unlock(&object->cookie->lock);
 404         _leave("");
 405 }
 406
 407 /*
 408  * look an object up in the cache from which it was allocated
 409  * - we hold an "access lock" on the parent object, so the parent object cannot
 410  *   be withdrawn by either party till we've finished
 411  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
 412  *   leaf-most cookies of the object and all its children
 413  */
 414 static void fscache_lookup_object(struct fscache_object *object)
 415 {
 416         struct fscache_cookie *cookie = object->cookie;
 417         struct fscache_object *parent;
 418
 419         _enter("");
 420
 421         parent = object->parent;
 422         ASSERT(parent != NULL);
 423         ASSERTCMP(parent->n_ops, >, 0);
 424         ASSERTCMP(parent->n_obj_ops, >, 0);
 425
 426         /* make sure the parent is still available */
 427         ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
 428
 429         if (parent->state >= FSCACHE_OBJECT_DYING ||
 430             test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
 431                 _debug("unavailable");
 432                 set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
 433                 _leave("");
 434                 return;
 435         }
 436
 437         _debug("LOOKUP \"%s/%s\" in \"%s\"",
 438                parent->cookie->def->name, cookie->def->name,
 439                object->cache->tag->name);
 440
 441         fscache_stat(&fscache_n_object_lookups);
 442         object->cache->ops->lookup_object(object);
 443
 444         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
 445                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 446
 447         _leave("");
 448 }
 449
 450 /**
 451  * fscache_object_lookup_negative - Note negative cookie lookup
 452  * @object: Object pointing to cookie to mark
 453  *
 454  * Note negative lookup, permitting those waiting to read data from an already
 455  * existing backing object to continue as there's no data for them to read.
 456  */
 457 void fscache_object_lookup_negative(struct fscache_object *object)
 458 {
 459         struct fscache_cookie *cookie = object->cookie;
 460
 461         _enter("{OBJ%x,%s}",
 462                object->debug_id, fscache_object_states[object->state]);
 463
 464         spin_lock(&object->lock);
 465         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 466                 fscache_stat(&fscache_n_object_lookups_negative);
 467
 468                 /* transit here to allow write requests to begin stacking up
 469                  * and read requests to begin returning ENODATA */
 470                 object->state = FSCACHE_OBJECT_CREATING;
 471                 spin_unlock(&object->lock);
 472
 473                 set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
 474                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 475
 476                 _debug("wake up lookup %p", &cookie->flags);
 477                 smp_mb__before_clear_bit();
 478                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 479                 smp_mb__after_clear_bit();
 480                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 481                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 482         } else {
 483                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 484                 spin_unlock(&object->lock);
 485         }
 486
 487         _leave("");
 488 }
 489 EXPORT_SYMBOL(fscache_object_lookup_negative);
 490
 491 /**
 492  * fscache_obtained_object - Note successful object lookup or creation
 493  * @object: Object pointing to cookie to mark
 494  *
 495  * Note successful lookup and/or creation, permitting those waiting to write
 496  * data to a backing object to continue.
 497  *
 498  * Note that after calling this, an object's cookie may be relinquished by the
 499  * netfs, and so must be accessed with object lock held.
 500  */
 501 void fscache_obtained_object(struct fscache_object *object)
 502 {
 503         struct fscache_cookie *cookie = object->cookie;
 504
 505         _enter("{OBJ%x,%s}",
 506                object->debug_id, fscache_object_states[object->state]);
 507
 508         /* if we were still looking up, then we must have a positive lookup
 509          * result, in which case there may be data available */
 510         spin_lock(&object->lock);
 511         if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
 512                 fscache_stat(&fscache_n_object_lookups_positive);
 513
 514                 clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 515
 516                 object->state = FSCACHE_OBJECT_AVAILABLE;
 517                 spin_unlock(&object->lock);
 518
 519                 smp_mb__before_clear_bit();
 520                 clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 521                 smp_mb__after_clear_bit();
 522                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
 523                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 524         } else {
 525                 ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 526                 fscache_stat(&fscache_n_object_created);
 527
 528                 object->state = FSCACHE_OBJECT_AVAILABLE;
 529                 spin_unlock(&object->lock);
 530                 set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 531                 smp_wmb();
 532         }
 533
 534         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
 535                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
 536
 537         _leave("");
 538 }
 539 EXPORT_SYMBOL(fscache_obtained_object);
 540
 541 /*
 542  * handle an object that has just become available
 543  */
 544 static void fscache_object_available(struct fscache_object *object)
 545 {
 546         _enter("{OBJ%x}", object->debug_id);
 547
 548         spin_lock(&object->lock);
 549
 550         if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
 551                 wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
 552
 553         fscache_done_parent_op(object);
 554         if (object->n_in_progress == 0) {
 555                 if (object->n_ops > 0) {
 556                         ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
 557                         ASSERTIF(object->n_ops > object->n_obj_ops,
 558                                  !list_empty(&object->pending_ops));
 559                         fscache_start_operations(object);
 560                 } else {
 561                         ASSERT(list_empty(&object->pending_ops));
 562                 }
 563         }
 564         spin_unlock(&object->lock);
 565
 566         object->cache->ops->lookup_complete(object);
 567         fscache_enqueue_dependents(object);
 568
 569         fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 570         fscache_stat(&fscache_n_object_avail);
 571
 572         _leave("");
 573 }
 574
 575 /*
 576  * drop an object's attachments
 577  */
 578 static void fscache_drop_object(struct fscache_object *object)
 579 {
 580         struct fscache_object *parent = object->parent;
 581         struct fscache_cache *cache = object->cache;
 582
 583         _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
 584
 585         spin_lock(&cache->object_list_lock);
 586         list_del_init(&object->cache_link);
 587         spin_unlock(&cache->object_list_lock);
 588
 589         cache->ops->drop_object(object);
 590
 591         if (parent) {
 592                 _debug("release parent OBJ%x {%d}",
 593                        parent->debug_id, parent->n_children);
 594
 595                 spin_lock(&parent->lock);
 596                 parent->n_children--;
 597                 if (parent->n_children == 0)
 598                         fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 599                 spin_unlock(&parent->lock);
 600                 object->parent = NULL;
 601         }
 602
 603         /* this just shifts the object release to the slow work processor */
 604         object->cache->ops->put_object(object);
 605
 606         _leave("");
 607 }
 608
 609 /*
 610  * release or recycle an object that the netfs has discarded
 611  */
 612 static void fscache_release_object(struct fscache_object *object)
 613 {
 614         _enter("");
 615
 616         fscache_drop_object(object);
 617 }
 618
 619 /*
 620  * withdraw an object from active service
 621  */
 622 static void fscache_withdraw_object(struct fscache_object *object)
 623 {
 624         struct fscache_cookie *cookie;
 625         bool detached;
 626
 627         _enter("");
 628
 629         spin_lock(&object->lock);
 630         cookie = object->cookie;
 631         if (cookie) {
 632                 /* need to get the cookie lock before the object lock, starting
 633                  * from the object pointer */
 634                 atomic_inc(&cookie->usage);
 635                 spin_unlock(&object->lock);
 636
 637                 detached = false;
 638                 spin_lock(&cookie->lock);
 639                 spin_lock(&object->lock);
 640
 641                 if (object->cookie == cookie) {
 642                         hlist_del_init(&object->cookie_link);
 643                         object->cookie = NULL;
 644                         detached = true;
 645                 }
 646                 spin_unlock(&cookie->lock);
 647                 fscache_cookie_put(cookie);
 648                 if (detached)
 649                         fscache_cookie_put(cookie);
 650         }
 651
 652         spin_unlock(&object->lock);
 653
 654         fscache_drop_object(object);
 655 }
 656
 657 /*
 658  * withdraw an object from active service at the behest of the cache
 659  * - need break the links to a cached object cookie
 660  * - called under two situations:
 661  *   (1) recycler decides to reclaim an in-use object
 662  *   (2) a cache is unmounted
 663  * - have to take care as the cookie can be being relinquished by the netfs
 664  *   simultaneously
 665  * - the object is pinned by the caller holding a refcount on it
 666  */
 667 void fscache_withdrawing_object(struct fscache_cache *cache,
 668                                 struct fscache_object *object)
 669 {
 670         bool enqueue = false;
 671
 672         _enter(",OBJ%x", object->debug_id);
 673
 674         spin_lock(&object->lock);
 675         if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
 676                 object->state = FSCACHE_OBJECT_WITHDRAWING;
 677                 enqueue = true;
 678         }
 679         spin_unlock(&object->lock);
 680
 681         if (enqueue)
 682                 fscache_enqueue_object(object);
 683
 684         _leave("");
 685 }
 686
 687 /*
 688  * allow the slow work item processor to get a ref on an object
 689  */
 690 static int fscache_object_slow_work_get_ref(struct slow_work *work)
 691 {
 692         struct fscache_object *object =
 693                 container_of(work, struct fscache_object, work);
 694
 695         return object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
 696 }
 697
 698 /*
 699  * allow the slow work item processor to discard a ref on a work item
 700  */
 701 static void fscache_object_slow_work_put_ref(struct slow_work *work)
 702 {
 703         struct fscache_object *object =
 704                 container_of(work, struct fscache_object, work);
 705
 706         return object->cache->ops->put_object(object);
 707 }
 708
 709 /*
 710  * enqueue an object for metadata-type processing
 711  */
 712 void fscache_enqueue_object(struct fscache_object *object)
 713 {
 714         _enter("{OBJ%x}", object->debug_id);
 715
 716         slow_work_enqueue(&object->work);
 717 }
 718
 719 /*
 720  * enqueue the dependents of an object for metadata-type processing
 721  * - the caller must hold the object's lock
 722  * - this may cause an already locked object to wind up being processed again
 723  */
 724 static void fscache_enqueue_dependents(struct fscache_object *object)
 725 {
 726         struct fscache_object *dep;
 727
 728         _enter("{OBJ%x}", object->debug_id);
 729
 730         if (list_empty(&object->dependents))
 731                 return;
 732
 733         spin_lock(&object->lock);
 734
 735         while (!list_empty(&object->dependents)) {
 736                 dep = list_entry(object->dependents.next,
 737                                  struct fscache_object, dep_link);
 738                 list_del_init(&dep->dep_link);
 739
 740
 741                 /* sort onto appropriate lists */
 742                 fscache_enqueue_object(dep);
 743                 dep->cache->ops->put_object(dep);
 744
 745                 if (!list_empty(&object->dependents))
 746                         cond_resched_lock(&object->lock);
 747         }
 748
 749         spin_unlock(&object->lock);
 750 }
 751
 752 /*
 753  * remove an object from whatever queue it's waiting on
 754  * - the caller must hold object->lock
 755  */
 756 void fscache_dequeue_object(struct fscache_object *object)
 757 {
 758         _enter("{OBJ%x}", object->debug_id);
 759
 760         if (!list_empty(&object->dep_link)) {
 761                 spin_lock(&object->parent->lock);
 762                 list_del_init(&object->dep_link);
 763                 spin_unlock(&object->parent->lock);
 764         }
 765
 766         _leave("");
 767 }
 768
 769 /**
 770  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
 771  * @object: The object to ask about
 772  * @data: The auxiliary data for the object
 773  * @datalen: The size of the auxiliary data
 774  *
 775  * This function consults the netfs about the coherency state of an object
 776  */
 777 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 778                                         const void *data, uint16_t datalen)
 779 {
 780         enum fscache_checkaux result;
 781
 782         if (!object->cookie->def->check_aux) {
 783                 fscache_stat(&fscache_n_checkaux_none);
 784                 return FSCACHE_CHECKAUX_OKAY;
 785         }
 786
 787         result = object->cookie->def->check_aux(object->cookie->netfs_data,
 788                                                 data, datalen);
 789         switch (result) {
 790                 /* entry okay as is */
 791         case FSCACHE_CHECKAUX_OKAY:
 792                 fscache_stat(&fscache_n_checkaux_okay);
 793                 break;
 794
 795                 /* entry requires update */
 796         case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 797                 fscache_stat(&fscache_n_checkaux_update);
 798                 break;
 799
 800                 /* entry requires deletion */
 801         case FSCACHE_CHECKAUX_OBSOLETE:
 802                 fscache_stat(&fscache_n_checkaux_obsolete);
 803                 break;
 804
 805         default:
 806                 BUG();
 807         }
 808
 809         return result;
 810 }
 811 EXPORT_SYMBOL(fscache_check_aux);